Form 3 & Cupping


I’ve recently been getting a lot of requests from clients who want to print “vase-like” parts that always flag the cupping warning in PreForm (think of a small rectangular container/box).

I’ve tried printing one of these on the Form 2 and noticed poor surface finish in some of the early layers. In a lot of cases I cannot add vent holes to alleviate the suction issue, so I’ve been having to print the parts in the opposite orientation, which results in a lot of supports internally which is annoying.

I’m just curious if the Form 3 is any better at dealing with cupping issues. I assume it would be the same because the problem is with suction and surface tension as opposed to the tank surface, but is there any improvement now that the peel event is purely in tension as opposed to shear + tension?


any process that involves lifting a part from a vat of liquid is going to have the cupping problem.

What you should do is orient the part in the way that gets the best quality surface on the Up side… and model a small hole at the lowest point.

Get yourself a 405nm laser pointer and simply use the resin and the laser to fill in the hole post print with the same resin.

or- model a tapered hole and a tapered plug that you can glue into the hole to seal it,
in which case the hole will have to be modeled oversize, as it will lose dimension in printing… but after you’ve done a few you can zero in on the size the hole and plug have to be in the model to get a very nice fit.

That’s an interesting idea, I hadn’t considered plugging the hole and sealing it, or just filling the hole and sealing it. I’d have to be careful not to make a mess and/or introduce mechanical inaccuracies, especially on the inside of the model where it’s difficult to sand.

Perhaps I can tape the inside of the hole and then fill the remaining space on the external side and cure using a 405nm laser and/or the cure station.

Do you know from experience how large of a vent hole is necessary? I think Formlabs said 3mm or something…

I used vent holes between 1 and 3mm, depending on the volume of the cup.

That being said, I think this has been discussed somewhere before and cupping wasn’t as bad or non-existent on the form 3 as the process of peeling each layer is very different.

Cupping is quite a bit better on the Form 3. The flexibility of the film in Form 3 means that pressure won’t build up in cups and cause the artifacts that are visible on Form 2. I’ve done a few cupped parts on our later prototypes that didn’t require any vent holes and didn’t have any print artifacts.


If cups are now less an issue with the Form3, it’s really a game changer… :slight_smile:

Thanks for that bit of info @Frew, that’s great to hear.

Will PreForm have different warning algorithms for the Form 3? Ie. will it complain less about cupping than Preform with a Form 2?